Optical receptacle with low transmission and photoelectric conversion module for the same

ABSTRACT

An optical receptacle with low transmission loss, which is connectable with an optical plug, is provided. The optical receptacle includes a photoelectric conversion module having the capability of making photoelectric conversion between light signals and electrical signals, and a module housing. The photoelectric conversion module is a molded interconnect device (MID), which is provided with a module body having a post, an optical device mounted on the post, and an electrical circuit mounted on the module body. The module housing has a tubular projection, into which an end of the optical fiber supported by the optical plug can be inserted. When the optical plug is connected with an optical receptacle, the end of the optical fiber is positioned in the tubular projection so as to be in a closely opposing relation to the optical device mounted on the post.

TECHNICAL FIELD

The present invention relates to an optical receptacle connectable withan optical plug having a light transmitting medium such as an opticalfiber, and a photoelectric conversion module for the optical receptacle,which has the capability of making photoelectric conversion betweenlight signals transmitted through the optical transmission medium andelectrical signals.

BACKGROUND ART

Worldwide developments of high-speed communication system preferablyused for transport means such as automobiles, airplanes, trains andshipping are now underway. For example, “MOST®” (Media Oriented SystemTransport) has been proposed as an optical communication standard inEurope.

FIG. 18 shows a conventional optical connector designed under the“MOST®” standard (“TYCO Electronics & MOST” in Presentations by MOSTmembers on “All Members Meeting Apr. 3, 2001”). This connector iscomposed of an optical receptacle 1P built in an electronic equipmentsuch as CD, DVD, GPS that can be used in the transport means, and anoptical plug 2P for supporting a pair of plastic optical fibers (POF)100. For example, when the optical plug 2 is connected to the opticalreceptacle 1, a data communication between the electronic equipment anda data base connected through the optical fibers becomes available inthe transport means.

The optical receptacle 1 can be mounted on a circuit board in theelectronic equipment, and is mainly composed of a pair of photoelectricconversion modules 10P having the capability of making photoelectricconversion between light signals transmitted through the optical fibers100 and electrical signals used in the electronic equipment, a shieldcase 50P made of a metal material for accommodating the photoelectricconversion modules, a pair of optical couplers 200 such as optical-fibermembers having a required length, each of which is placed between anoptical device of the photoelectric conversion module 10P and an end ofthe optical fiber 100 supported by the optical plug 2P, optical-fiberhousing 80 for accommodating these optical couplers therein, and areceptacle housing 40P for providing a space for making the connectionbetween the optical plug 2P and the optical coupler 200.

One of the photoelectric conversion modules 10P has the capability ofconverting the optical signals transmitted through the optical fiber 100to the electric signals, and the other one has the capability ofconverting the electric signals provided from the electronic equipmentto the optical signals to be supplied to the optical fiber. As shown inFIG. 19, each of the photoelectric conversion modules 10P is providedwith an optical device 12P such as light-emitting diode andlight-receiving diode, and an electric circuit 14P electricallyconnected to the optical device by a lead wire 16P. After the opticaldevice 12P and the electric circuit 14P are mounted on a single leadframe 90, they are integrally molded with a translucent resin 11P toobtain a resin molded article 95 having a substantially rectangularsolid shape. When the optical plug 2P is connected to the opticalreceptacle 1P, the optical signals provided from the optical fibers 100of the optical plug are transmitted to the optical devices 12P of thephotoelectric conversion modules 10P through the optical couplers 200.

In addition, Japanese Patent Early Publication [kokai] No. 2001-13367discloses an optical receptacle, as shown in FIG. 20. This opticalreceptacle is provided with a receptacle housing 40E having a frontopening 41E, into which an optical plug (not shown) can be fitted,optical device modules 10E, a pair of sleeves 85 that are useful toimprove production efficiency of the optical receptacle, and a cap 50E.The receptacle housing also has a rear opening 43E, through which theoptical device modules 10E and the sleeves 85 are accommodated in thereceptacle housing 40E.

The optical device modules 10E and the sleeves 85 are placed in thereceptacle housing 40E such that when the optical plug is connected tothe optical receptacle 1E, each of the top ends of the optical fiberssupported by the optical plug is positioned in an opposing relation withthe corresponding optical device module 10E through the sleeve 85. Thesleeve 85 is composed of an optical waveguide portion made of glass orsynthetic resin, and a cylindrical holder portion made of a metalmaterial. Alternatively, an additional optical fiber having a requiredlength may be used as the sleeve 85.

According to this optical receptacle, since the optical device module10E is smoothly fitted in the receptacle housing 40E by use of thesleeve 85, it is possible to prevent the optical device module 10E frombeing inserted in an oblique direction into the receptacle housing, andalso from a breakage caused by an accidental interference with thereceptacle housing. Therefore, there is an advantage that productionefficiency and yield of the optical receptacle are improved, as comparedwith conventional cases.

However, in the conventional optical receptacles described above, sincethe optical couplers 200 such as the optical-fiber members having therequired length or the sleeves 85 are disposed between the top ends ofthe optical fibers supported by the optical plug and the optical devicesof the optical receptacle, an increase in transmission loss of theoptical signals comes into a problem. In addition, there is anotherproblem of increasing total component counts of the optical receptacle.

SUMMARY OF THE INVENTION

In consideration of the above-described problems, the present inventionprovides an optical receptacle with low transmission loss, which isconnectable with an optical plug having an optical transmission mediumnot through an additional transmission medium such as sleeve or anadditional optical fiber.

That is, the optical receptacle of the present invention comprises aphotoelectric conversion module having the capability of makingphotoelectric conversion between light signals transmitted through theoptical transmission medium and electrical signals, and a module housingfor accommodating the photoelectric conversion module therein. Themodule housing is formed with a tubular projection, into which one endof the optical transmission medium can be inserted. The photoelectricconversion module comprises an optical device disposed in a closelyopposing relation to the one end of the optical transmission medium inthe tubular projection when the optical plug is connected with theoptical receptacle, and an electrical circuit electrically connected tothe optical device. For example, the optical device may be at least oneof a light emitting element and a light receiving element.

According to the present invention, since the optical device of theoptical receptacle is disposed in a closely opposing relation to the oneend of the optical transmission medium supported by the optical plug inthe tubular projection without using the additional optical fiber or thesleeve, it is possible to conduct optical data communications betweenthe optical transmission medium and the optical device with a reducedtransmission loss.

It is preferred that module housing has the tubular projectionintegrally formed on its front surface, a rear opening, through whichthe photoelectric conversion module is accommodated in the modulehousing, and a shield layer formed on its exterior surface. In thiscase, by the formation of the shield layer on the exterior surface ofthe module housing, it is possible to reduce component counts, downsizethe optical receptacle as whole, and also improve resistance to noise.

It is also preferred that the photoelectric conversion module comprisesa module body having a post, on a top of which the optical device ismounted, and the electric circuit is mounted on the module body. Inparticular, it is preferred that the post is formed in its top with arecess for mounting the optical device on a bottom of the recess, and areflection layer for preventing a scattering of light is formed on asidewall in the recess. In this case, since the reflection layereffectively prevents the scattering of light, it is possible to furtherreduce the transmission loss.

It is further preferred that the module housing has a stopper formed inthe tubular projection, against which the one end of the opticaltransmission medium abuts when the optical plug is connected with theoptical receptacle. In this case, it is possible to minimize variationsin distance (gap) between the optical device and the opticaltransmitting medium, and stably provide a constant optical couplingefficiency therebetween.

Moreover, it is preferred that a lens is positioned between the opticaldevice and the one end of the optical transmission medium when theoptical plug is connected with the optical receptacle. In this case, thelens can improve the optical coupling efficiency therebetween. Inaddition, even when the distance (gap) between the optical device andthe optical transmission medium accidentally increases, it is possibleto minimize fluctuations of transmission loss.

In addition, it is preferred that the photoelectric conversion module isa molded interconnect device (MID) that a wiring for making electricalconnection between the optical device and the electrical circuit isformed along an exterior surface of the module body. In this case, it ispossible to reduce component counts, shorten assembly times, and achievedownsizing and light-weighting of the photoelectric conversion module.

As a particularly preferred embodiment of the present invention, theoptical receptacle comprises a photoelectric conversion module havingthe capability of making photoelectric conversion between light signalstransmitted through the optical transmission medium and electricalsignals, and a module housing for accommodating the photoelectricconversion module therein. The photoelectric conversion module comprisesa module body having a post, an optical device mounted on a top of thepost, and an electrical circuit mounted on the module body andelectrically connected to the optical device. The module housing has atubular projection, into which one end of the optical transmissionmedium can be inserted, and a partition wall is formed in the tubularprojection. The photoelectric conversion module is accommodated in themodule housing such that the post is positioned at a side of saidpartition wall in the tubular projection. When the optical plug isconnected with the optical receptacle, the one end of the opticaltransmission medium is positioned at the opposite side of the partitionwall in the tubular projection so as to be in a closely opposingrelation to the optical device mounted on the post.

According to this optical receptacle of the present invention, it ispossible to provide the following advantage in addition to theabove-described advantage of reducing the transmission loss. That is,when the optical plug is connected to the optical receptacle, theoptical transmission medium supported by the optical plug can beinserted into the tubular projection such that the top end of theoptical transmission medium abuts against the partition wall. In otherwords, the partition wall functions as a stopper for the opticaltransmission medium. Therefore, it is possible to minimize variations indistance (gap) between the optical device and the optical transmittingmedium, and stably provide a constant optical coupling efficiencytherebetween.

As a further preferred embodiment of the present invention, the opticalreceptacle comprises a receptacle housing for accommodating the modulehousing therein, which is used for connection with the optical plug, andhas a front opening, through which the optical plug can be inserted intoa plug accommodation space defined in the receptacle housing, a rearopening, through which the photoelectric conversion module isaccommodated in the receptacle housing such that the tubular projectionof the module housing projects in the plug accommodation space, and therear opening is closed by an electromagnetic interference shieldingmember. In particular, when the photoelectric conversion module isprevented from the electromagnetic interference by the shielding memberin cooperation with the above-described shield layer formed on theexterior surface of module housing, it is possible to provide excellentresistance to noise.

A further concern of the present invention is to provide a photoelectricconversion module for the optical receptacle with low transmission loss,which is connectable with an optical plug having an optical transmissionmedium not through an additional transmission medium. That is, thephotoelectric conversion module has the capability of makingphotoelectric conversion between light signals transmitted through theoptical transmission medium and electrical signals, and comprises amodule body having a post, an optical device mounted on a top of thepost, and an electrical circuit mounted on the module body andelectrically connected to the optical device. The photoelectricconversion module is a molded interconnect device (MID) that a wiringfor making the electrical connection between the optical device and theelectrical circuit is formed along an exterior surface of said modulebody. The optical device mounted on the post is disposed in a closelyopposing relation to one end of the optical transmission medium when theoptical plug is connected with the optical receptacle.

Since the photoelectric conversion module of the present invention isthe molded interconnect device (MID), which is characterized in that theelectrical circuit and the optical device are mounted on the modulebody, e.g., a three-dimensional molded resin article, and the electriccircuit is electrically connected to the optical device by the wiringpattern three-dimensionally formed along the exterior of the modulebody, it is possible to reduce component counts, and shorten assemblytimes. In-addition, by enabling higher mounting density, it is possibleto achieve downsizing and light-weighting of the photoelectricconversion module, and therefore reduce size of the optical receptacle.

These and still other objects and advantages of the present inventionwill become more apparent from the best mode for carrying out theinvention explained below, referring to the attached drawings.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is an exploded perspective view of an optical receptacleaccording to a preferred embodiment of the present invention;

FIG. 2 is a perspective view of photoelectric conversion modules of theoptical receptacle;

FIG. 3 is a cross-sectional view of the photoelectric conversion moduleaccommodated in a module housing;

FIG. 4 is a magnified cross-sectional view of a part of FIG. 3;

FIG. 5 is an elevational view partly in section of the photoelectricconversion module;

FIG. 6 is a perspective view of the module housing;

FIG. 7 is an exploded rear perspective view of a photoelectricconversion module;

FIG. 8 is an exploded front perspective view of the photoelectricconversion module;

FIG. 9 is a rear plan view of the photoelectric conversion module;

FIG. 10 is a partially bottom plan view of the photoelectric conversionmodule;

FIG. 11 is an elevational view partly in section of the photoelectricconversion module accommodated in the module housing;

FIG. 12 is a perspective view of a receptacle housing with anelectromagnetic interference shielding member;

FIG. 13 is a partially cross-sectional view of the optical receptacle ofthe present. embodiment;

FIGS. 14A to 14D are perspective views illustrating a method ofattaching the shielding member to the receptacle housing;

FIG. 15 is a graph showing an influence of the presence or absence of alens and a reflection layer in the optical receptacle over transmissionloss;

FIG. 16 is a graph showing a correspondence between simulation resultsand actually measured results with regard to the transmission loss;

FIG. 17 is a perspective view of the photoelectric conversion moduleaccording to a modification of the above embodiment;

FIG. 18 is an exploded perspective view of a conventional opticalreceptacle;

FIG. 19 is a cross-sectional view of a photoelectric conversion moduleof the optical receptacle of FIG. 18; and

FIG. 20 is an exploded perspective view of another conventional opticalreceptacle.

BEST MODE FOR CARRYING OUT THE INVENTION

An optical receptacle according to a preferred embodiment of the presentinvention is explained in detail below.

<First Embodiment>

As shown in FIG. 1, the optical receptacle 1 of this embodiment isconnectable with an optical plug 2 supporting one ends of a pair ofplastic optical fibers (POF) 110 as an optical transmission medium, andpreferably used for data communication between a data base connectedthrough the other ends of the optical fibers 110 and an on-boardelectric equipment such as CD, DVD, GPS and car telephone.

As shown in FIGS. 1 and 2, the optical receptacle 1 is mainly composedof a pair of photoelectric conversion modules 10 each having thecapability of making photoelectric conversion between light signalstransmitted through the optical fibers 100 and electrical signals usedin the electrical equipment, a module housing 30 of a resin moldedarticle for accommodating the photoelectric conversion modules 10therein, a receptacle housing 40 for accommodating the module housing 30therein, and an electromagnetic interference shielding member 50 made ofa metal material.

The photoelectric conversion module 10 can be mounted on a circuit boardbuilt in the electric equipment. One of the photoelectric conversionmodules 10 is a first photoelectric conversion module with an opticaldevice such as a light-receiving diode (PD), which has the capability ofconverting received light signals into electrical signals. The other oneis a second photoelectric conversion module with another optical devicesuch as a light-emitting diode (LED), which has the capability ofconverting electrical signals into light signals and projecting thelight signals to the optical fiber 100.

As shown in FIGS. 2 and 3, each of the photoelectric conversion modules10 comprises a module body 20 having a column-shaped post 21, theabove-described optical device 12 attached to a top of the post, and anelectrical circuit 14 mounted on the module body and electricallyconnected to the optical device. For example, the module body 20 may beconfigured in a substantially rectangular solid. The post 21 isintegrally formed on a front surface of the module body 20. The post 21is formed in its top with a recess 22 for mounting the optical device ona bottom of the recess.

The optical device 12 mounted in the recess 22 is sealed with atranslucent resin 11. The translucent resin is molded in a shape ofconvex lens 13. That is, the convex lens 13 for the first photoelectricconversion module is formed such that light provided from the opticalfiber 100 is focused on a light receiving surface of the optical device12 by the convex lens 13. On the other hand, the convex lens 13 for thesecond photoelectric conversion module is formed such that lightprovided from the light-emitting diode (LED) of the optical device 12 isincident on the optical fiber 100 as parallel light beam. In particular,it is preferred that the convex lens 13 is formed on the optical device12 by molding a translucent insulating resin at the top of the post 21,and the post has an insulating protective layer 19 formed by coating thetranslucent insulating resin on a side wall of the post, at which awiring pattern described later extends to make an electrical connectionbetween the optical device 12 and the electrical circuit 14.

As shown in FIG. 4, a side of the recess 22 is of a curved surface, onwhich a metal plating layer is formed as a reflection layer 15 forpreventing a scattering of light. That is, the reflection layer 15 forthe first photoelectric conversion module reflects the light providedfrom the optical fiber 100, so that the reflected light is incident onthe light-receiving diode (PD) of the optical device 12. On the otherhand, the reflection layer 15 for the second photoelectric conversionmodule reflects the light provided from the light-emitting diode (LED)of the optical device 12, so that the reflected light is incident on theoptical fiber 100. Thus, since the reflection layer 15 prevents thescattering of light, it is possible to reduce coupling loss.

As shown in FIG. 5, the module body 20 is formed in a rear surface witha concave 23 for mounting the electrical circuit 14 on a bottom of theconcave. In the case of the first photoelectric conversion module, theelectrical circuit 14 comprises an integrated circuit, in which an inputcircuit for receiving output signals of the light-receiving diode (PD)is formed, and circuit components such as chip capacitors. On the otherhand, in the case of the second photoelectric conversion module, theelectrical circuit 14 comprises an integrated circuit, in which anoutput circuit for providing drive signals to the light-emitting diode(LED) is formed, and the circuit components such as chip capacitors.

The photoelectric conversion module 10 is a molded interconnect device(MID) that the wiring pattern 16 for making the electrical connectionbetween the optical device 12 and the electrical circuit 14 is formedalong an exterior surface of the module body 20.

In this embodiment, as shown in FIG. 5, the module body 20 has a throughhole 24 extending between a position adjacent to the post 21 on thefront surface of the module body and a position close to the electricalcircuit 14 mounted in the concave 23. A metal plating layer is formed asthe wiring pattern 24 along a side of the post 21 and an interiorsurface of the through hole 24 such that the optical device 12 mountedon the top of the post is electrically connected to the electricalcircuit 14. In addition, after mounting the electrical circuit 14, andforming the wiring pattern 24, a sealing resin 25 is filled in theconcave 23 of the module body 20.

As shown in FIG. 6, the module housing 30 is a resin molded articlehaving a pair of tubular projections 31 integrally formed on its frontsurface, into which one end of the optical fibers 100 of the opticalplug 2 can be inserted, a rear opening 32, through which thephotoelectric conversion modules 10 are accommodated in the modulehousing, and a shield layer 33 formed on its exterior surface by metalplating.

In addition, as shown in FIG. 7, the module housing 30 has a separationwall 34 therein, by which a first room used to accommodate one of thephotoelectric conversion modules 10 therein is spaced from a second roomfor accommodating the other photoelectric conversion module 10 therein.The first and second rooms are respectively communicated with interiorspaces of the tubular projections 31.

In the tubular projections 31, a partition wall 35 having a centeraperture 36 is formed such that an optical-fiber receiving space “S2”defined at one side (right side of FIG. 4) of the partition wall 35 toreceive the end of the optical fiber 100 supported by the optical plug 2is communicated with a post receiving space “S1” defined at the oppositeside (left side of FIG. 4) of the partition wall 35 to receive the post21 of the module body 20 through the center aperture 36.

Each of the photoelectric conversion modules 10 can be accommodated inthe module housing 30 according to the following procedure. First, asshown in FIGS. 7 and 8, a plurality of L-shaped terminal pins 60 areattached to terminal holes 26 formed in the rear surface of the modulebody 20. That is, when one end of each of the terminal pins 60 arepushed in the terminal hole 26, the terminal pin is electricallyconnected to a wiring 17 formed on the module body 20 by metal platingto make an electrical connection between an interior surface in theterminal hole 26 and the electrical circuit 14 mounted on the modulebody 20.

In this embodiment, two kinds of L-shape terminal pins (60 a, 60 b)having long and short arms (61 a, 61 b) are staggered in the directionof arrangement of the terminal holes 26. That is, when all of theterminal pins are pushed in the terminal holes, legs (62 a, 62 b) of theterminal pins are spaced away from each other by a distance “d1” in thetransverse direction of the module body 20, as shown in FIG. 9, and alsoeach of the legs (62 a, 62 b) are spaced away from the adjacent leg by adistance “d2” in the forward and backward direction of the module body20, as shown in FIG. 10.

After fixing the terminal pins 60 to the module body 20, thephotoelectric conversion modules 10 are placed in the module housing 30through the rear opening 32 such that the post 21 of the module body isaccommodated in the post receiving space “S1” in the tubular projection31 of the module housing, and the side surface of the post 21 fits theinterior surface of the tubular projection 31, as shown in FIG. 11. Atthis time, a lens 13 is placed between the partition wall 35 of themodule housing 30 and the post 21 having the optical device 12, as shownin FIGS. 3 and 4. In other words, the top of the post abuts against aside surface of the partition wall 35 through the lens 13, and a convexportion of the lens 13 projects into the center aperture 36 of thepartition wall.

After accommodating the photoelectric conversion modules 10 in themodule housing 30, a sealing resin 27 is filled in the module housing,as shown in FIG. 3. In FIG. 3, the numeral 28 designates a locating tabformed adjacent to the post 21 on a front surface of the module body 20.By fitting the locating tab 28 into a locating slot 37 formed in themodule housing 30, it is possible to accurately accommodate thephotoelectric conversion module 10 at a desired position in the modulehousing 30.

As shown in FIGS. 12 and 13, the receptacle housing 40 is a moldedarticle of synthetic resin, which has a front opening 41, through whichthe optical plug 2 can be inserted into a plug accommodation room R1defined in the receptacle housing, a rear opening 43, through which thephotoelectric conversion modules 10 are accommodated in a moduleaccommodating room R2 defined in the receptacle housing such that thetubular projections 31 of the module housing 30 projects in the plugaccommodation space. R1. The rear opening 43 is closed by theelectromagnetic interference shielding member 50.

The shielding member 50 can be formed by punching and bending a metalsheet, which is composed of a cover plate 51 having a rectangular shape,a pair of claws 52 extending forwardly from both sides of the coverplate, three earth terminals 53 extending downwardly from the bottom endof the cover plate, and three contact segments 54 formed in the coverplate. In FIG. 13, the numeral 46 designates a pair of through holesformed in the receptacle housing 40, into which the tubular projections31 of the module housing 30 can be inserted, and the numeral 47designates an engaging slot formed adjacent to the front opening 41 inthe top surface of the receptacle housing.

The module housing 30 having the photoelectric conversion modules 10therein can be accommodated in the receptacle housing 40 according tothe following procedure. First, as shown in FIG. 14A, the module housing30 is placed in the module accommodating room R2 of the receptaclehousing such that the tubular projections 31 project into the plugaccommodating room R1 through the through holes 46 of the receptaclehousing 40. At this time, each of the L-shaped terminal pins 60supported by the module body 20 is fitted into a groove 48 formed in abottom wall of the receptacle housing 40, as shown in FIG. 14B.

Next, the shielding member 50 is secured to the receptacle housing 40 byfitting the claws 52 in a pair of engaging holes 42 formed in the topsurface of the receptacle housing, as shown in FIG. 14C, while putting apair of pins 56 formed on the bottom end of the cover plate 51 of theshielding member 50 in pockets 49 formed at the vicinity of the rearopening 43 of the receptacle housing 40, as shown in FIG. 14D. At thistime, the contact segments 54 of the shielding member 50 contact theshield layer 33 formed on the exterior surface of the module housing 30.Therefore, when the shielding member 50 is connected to ground throughthe earth terminals 53, it is possible to connect the shield layer 33 tothe ground through the shielding member 50. In addition, since each ofthe contact segments 54 is pressed against the shield layer 33 on themodule housing 30 by its spring force, it is possible to achieve areliable contact between the shielding member 50 and the shield layer33. Moreover, since the photoelectric conversion modules 10 areprevented from electromagnetic interference by the presence of theshielding member 50 and the shield layer 33, excellent resistance tonoise is obtained.

Thus, the shielding member 50 closes the rear opening 43 of thereceptacle housing 40 to prevent a fall of the photoelectric conversionmodules 10 from the receptacle housing, and also function as theelectromagnetic interference shielding means in cooperation with theshield layer 33 formed on the module body 30. Therefore, there areadvantages of reducing total component counts of the optical receptacle1, and downsizing the optical receptacle as whole, as compared with thecase of separately forming a cover for closing the rear opening of thereceptacle housing and a shielding member for protecting thephotoelectric conversion modules from the electromagnetic interference.

Next, the optical plug 2 connectable with the optical receptacle 1 ofthe present embodiment is explained. In this embodiment, shape and sizeof an engaging portion of the optical plug 2 with the optical receptacle1 are determined according to the “MOST®” standard.

The optical plug 2 is a resin molded article, and is formed with a plugbody 70 having a shape that can be fitted the front opening 41 of thereceptacle housing 40. The pair of optical fibers 100 are supported inparallel in the plug body 70. The plug body has an engagement lever 71on its top surface, which is used to lock or release the engagementbetween the optical receptacle 1 and the optical plug 2. One end of theengagement lever 71 is connected to the plug body 70, and a release tab72 is formed at the vicinity of an opposite free end of the engagementlever. When pushing down the release tab 72, the engagement lever 71 canbe elastically deformed. The engagement lever 71 also has a pair ofknobs 73 formed adjacent to the release tab 72, which can be engaged inthe engaging slot 47 of the receptacle housing 40.

When the optical plug 2 is connected to the optical receptacle 1, thetop ends of the pair of optical fibers 100 are inserted into theoptical-fiber receiving space “S2” of the tubular projections 31 of themodule housing 30. At this time, since the top end of each of theoptical fibers 100 abuts against the side surface of the partition wall35 in the tubular projection 31, the partition wall can prevent theoccurrence of an accidental interference between the optical fiber 100and the optical device 12. In addition, the partition wall functions asa stopper for inserting the optical fiber at a required depth in thetubular projection 31 with good repeatability. For example, when thepartition wall 35 is not formed in the tubular projection 31, thedistance (gap) between the top end of the inserted optical fiber 100 andthe optical device 12 fluctuates in a range of about 1.5 mm. On theother hand, when the partition wall 35 is formed in the tubularprojection, the distance therebetween fluctuates in a smaller range ofabout 0.7 mm. This result suggests that the formation of the partitionwall 35 is effective to more stably provide optical data communicationwith low transmission loss. Thus, the optical receptacle 1 having thepartition wall 35 corresponds to one of particularly preferredembodiments of the present invention.

By the way, as described above, when the optical plug 2 is connected tothe optical receptacle 1, the top end of each of the optical fibers 100abuts against the side surface of the partition wall 35, and the post 21of the module body 20 abuts against the opposite side surface of thepartition wall 35 through the lens 13. This means that the top end ofthe inserted optical fiber 100 is positioned in a closely opposingrelation to the optical device 12 mounted on the post 21 in the tubularhousing 31. Therefore, in the present invention, since it is notnecessary to arrange an additional optical fiber or an additional partsuch as sleeve between the optical device 12 and the optical fiber 100supported by the optical plug 2, the distance (gap) therebetween becomessmaller, so that a considerable reduction in transmission loss can beachieved.

When the optical plug 2 is connected to the optical receptacle 1, theknobs 73 formed on the engagement lever 71 fit in the engaging slot 47of the receptacle housing 40 to lock the connection between the opticalplug and the optical receptacle. To improve easiness of locking theconnection therebetween, it is preferred that each of the knobs 73 has afirst inclined surface 75 for smoothly guiding the knobs into theengaging slot 47, as shown in FIG. 13. On the other hand, the connectionbetween the optical plug 2 and the optical receptacle 1 can be releasedby pulling out the optical plug from the plug accommodation room R1 inthe receptacle housing 40, while pushing down the release tab 72 toremove the knobs 73 from the engaging slot 47. To improve easiness ofreleasing the connection therebetween, it is preferred that each of theknobs 73 has a second inclined surface 76 formed at the opposite side ofthe first inclined surface 75 to smoothly guide the knobs from theengaging slot 47 to the outside, as shown in FIG. 12.

Next, simulation results of evaluating an influence of the presence orabsence of the lens 13 and reflection layer 15 of the optical receptacle1 over an amount of optical output supplied from the optical device 12,i.e., the light-emitting diode (LED) to the optical fiber 100 areexplained. That is, the simulation results of FIG. 15 were obtained bymeasuring relationships between an optical amount received by theoptical fiber 100 and a distance (gap) between the light-emitting diode(LED) and the end surface of the optical fiber 100 under a conditionthat an optical output from the light-emitting diode (LED) is constant.In FIG. 15, the curve “C1” corresponds to the simulation resultsobtained by use of the optical receptacle 1 having the lens 13 and thereflection layer 15, and the curve “C2” corresponds to the simulationresults obtained by use of the optical receptacle not having the lensand the reflection layer.

In the simulation results of FIG. 15, when the optical receptacle nothaving the lens and reflection layer is used, and the gap is 1 mm, theoptical amount received by the optical fiber 100 is 1. On the otherhand, when the optical receptacle having the lens 13 and reflectionlayer 15 is used, and the gap is 1 mm, the optical amount received bythe optical fiber 100 is 1.8, which is much larger than the case ofusing the optical receptacle not having the lens and reflection layer.

Moreover, in the case of using the optical receptacle not having thelens and reflection layer, as the gap increases from 1 mm to 1.3 mm, theoptical amount received by the optical fiber 100 reduces from 1 to 0.6.This means that the optical amount received by the optical fiber 100reduces by 40% on the change in the gap. On the other hand, in the caseof using the optical receptacle 1 having the lens 13 and reflectionlayer 15, as the gap increases from 1 mm to 1.3 mm, the optical amountreceived by the optical fiber 100 reduces from 1.8 to 1.65. This meansthat the optical amount received by the optical fiber 100 reduces byonly 8% on the change in the gap.

These simulation results mean that the formation of the lens 13 andreflection layer 15 is effective to minimizing the transmission loss andfurther increase the optical amount received by the optical fiber 100.Therefore, the optical receptacle 1 having the lens 13 and thereflection layer 15 corresponds to one of particularly preferredembodiments of the present invention.

FIG. 16 is a graph showing relationships between the transmission lossand the distance (gap) between the optical device 12 and the end surfaceof the optical fiber 100. In this graph, the solid line corresponds tosimulation results, and rectangular dots “□” correspond to actuallymeasured results. The simulation results are in good agreement with themeasured results.

As a modification of the above embodiment, in place of the wiringpattern 16 shown in FIG. 5, another wiring pattern 18 may be formed onthe side of the post 21, the front, side and rear surfaces of the modulebody 20 by metal plating, as shown in FIG. 17, to electrically connectthe optical device 12 to the electrical circuit 14 mounted on the modulebody 20 without forming the through hole 24 in the module body.

As a further modification of the above embodiment, in place of formingthe locating tab 28 of the module body 20, the positioning of the modulebody in the module housing 30 may be performed by appropriatelydesigning a clearance between the interior surface of the tubularprojection 31 and the exterior surface of the post 21 of the module body20, or a clearance between the interior surface of the module housing 30and the exterior surface of the module body 20. In this case, since themodule housing 30 not having the locating slots 37 is provided, it ispossible to further improve the electromagnetic interference shieldingeffect of the module housing.

INDUSTRIAL APPLICABILITY

As understood from the above explanation, since it is not necessary toarrange an additional optical fiber or an additional part such as sleevebetween the optical device and the optical fiber supported by theoptical plug, the optical receptacle of the present invention canprovide a low transmission loss by minimizing a distance (gap) betweenthe top end of the optical fiber supported by the optical plug and theoptical device when the optical receptacle is connected to the opticalplug. In addition, since the electrical circuits such as integratedcircuits and circuit components are mounted on the rear surface of themodule body, and the optical device is mounted to the post formed on thefront surface of the module body, there is an advantage that the opticalreceptacle can be readily assembled. Moreover, when the photoelectricconversion module is surrounded with the shield layer formed on theexterior surface the module body and the electromagnetic interferenceshielding member, it is possible to effectively prevent thephotoelectric conversion module from the electromagnetic interferenceand provide excellent resistance to noise.

Therefore, the optical receptacle of the present invention having thecapability of achieving the above-described advantages will be widelyuseful in the technical field of a high-speed optical communication, andpreferably used for various transport means such as automobiles,airplanes, trains and shipping.

1. An optical receptacle connectable with an optical plug having anoptical transmission medium, said optical receptacle comprising aphotoelectric conversion module having the capability of makingphotoelectric conversion between light signals transmitted through saidoptical transmission medium and electrical signals, and a module housingfor accommodating said photoelectric conversion module therein, whereinsaid module housing is formed with a tubular projection, into which oneend of said optical transmission medium can be inserted, and saidphotoelectric conversion module comprises an optical device disposed ina closely opposing relation to the one end of said optical transmissionmedium in said tubular projection when said optical plug is connectedwith said optical receptacle, and an electrical circuit electricallyconnected to said optical device.
 2. The optical receptacle as set forthin claim 1, wherein said optical device is at least one of a lightemitting element and a light receiving element.
 3. The opticalreceptacle as set forth in claim 1, wherein said module housing has saidtubular projection integrally formed on its front surface, a rearopening, through which said photoelectric conversion module isaccommodated in said module housing, and a shield layer formed on itsexterior surface.
 4. The optical receptacle as set forth in claim 1,wherein said module housing has a stopper formed in said tubularprojection, against which the one end of said optical transmissionmedium abuts when said optical plug is connected with said opticalreceptacle.
 5. The optical receptacle as set forth in claim 1, furthercomprising a lens, which is positioned between said optical device andthe one end of said optical transmission medium when said optical plugis connected with said optical receptacle.
 6. The optical receptacle asset forth in claim 1, wherein said photoelectric conversion modulecomprises a module body having a post, on a top of which said opticaldevice is mounted, and said electric circuit is mounted on said modulebody.
 7. The optical receptacle as set forth in claim 6, wherein saidpost is formed in its top with a recess for mounting said optical deviceon a bottom of said recess, and a reflection layer for preventing ascattering of light is formed on a sidewall in said recess.
 8. Theoptical receptacle as set forth in claim 1, further comprising areceptacle housing for accommodating said module housing therein, whichis used for connection with said optical plug and has a front opening,through which said optical plug can be inserted into a plugaccommodation space defined in said receptacle housing.
 9. The opticalreceptacle as set forth in claim 8, wherein said receptacle housing hasa rear opening, through which said photoelectric conversion module isaccommodated in said receptacle housing such that said tubularprojection of said module housing projects in said plug accommodationspace, and said rear opening is closed by an electromagneticinterference shielding member.
 10. The optical receptacle as set forthin claim 6, wherein said photoelectric conversion module is a moldedinterconnect device that a wiring for making electrical connectionbetween said optical device and said electrical circuit is formed alongan exterior surface of said module body.
 11. The optical receptacle asset forth in claim 6, wherein said photoelectric conversion module has alens formed on said optical device by molding a translucent insulatingresin at the top of said post, and an insulating protective layerobtained by coating said translucent insulating resin on a side wall ofsaid post, at which a wiring pattern is formed to make an electricalconnection between said optical device and said electrical circuit. 12.An optical receptacle connectable with an optical plug having an opticaltransmission medium, said optical receptacle comprising a photoelectricconversion module having the capability of making photoelectricconversion between light signals transmitted through said opticaltransmission medium and electrical signals, and a module housing foraccommodating said photoelectric conversion module therein, wherein saidphotoelectric conversion module comprises a module body having a post,an optical device mounted on a top of said post, and an electricalcircuit mounted on said module body and electrically connected to saidoptical device, said module housing has a tubular projection, into whichone end of said optical transmission medium can be inserted, and apartition wall is formed in said tubular projection, said photoelectricconversion module is accommodated in said module housing such that saidpost is positioned at a side of said partition wall in said tubularprojection, and wherein when said optical plug is connected with saidoptical receptacle, the one end of said optical transmission medium ispositioned at the opposite side of said partition wall in said tubularprojection so as to be in a closely opposing relation to said opticaldevice mounted on said post.
 13. A photoelectric conversion module foran optical receptacle connectable with an optical plug having an opticaltransmission medium, said photoelectric conversion module having thecapability of making photoelectric conversion between light signalstransmitted through said optical transmission medium and electricalsignals, and comprising a module body having a post, an optical devicemounted on a top of said post, and an electrical circuit mounted on saidmodule body and electrically connected to said optical device, whereinsaid photoelectric conversion module is a molded interconnect devicethat a wiring for making the electrical connection between said opticaldevice and said electrical circuit is formed along an exterior surfaceof said module body, and said optical device mounted on said post isdisposed in a closely opposing relation to one end of said opticaltransmission medium when said optical plug is connected with saidoptical receptacle.